The Collaborative International Dictionary of English v.0.48:

Affectation \Af`fec*ta"tion\, n. [L. affectatio: cf. F.
   affectation.]
   1. An attempt to assume or exhibit what is not natural or
      real; false display; artificial show. "An affectation of
      contempt." --Macaulay.
      [1913 Webster]

            Affectation is an awkward and forced imitation of
            what should be genuine and easy, wanting the beauty
            that accompanies what is natural what is natural.
                                                  --Locke.
      [1913 Webster]

   2. A striving after. [Obs.] --Bp. Pearson.
      [1913 Webster]

   3. Fondness; affection. [Obs.] --Hooker.
      [1913 Webster]

WordNet (r) 3.0 (2006):

affectation
    n 1: a deliberate pretense or exaggerated display [syn:
         affectation, mannerism, pose, affectedness]